I used to think that the greatest threat to tackling climate change was the group of deniers holding us back from building a consensus around the problem and how to deal with it. Now I fear the greatest threat is defeatism dressed up as idealism.

The Green party pretends to be idealistic and ambitious but encourages defeatism with its complete refusal to accept that there has been progress in tackling climate change. Not least of all the Climate Change Act; a world first, binding the UK government by law to reduce carbon emissions by a third by 2020 and by 80% by 2050. It's a model that Friends of the Earth campaign for other countries to adopt in their Big Ask, a sign perhaps of greater optimism and ambition than the Green party demonstrates.

With an ambitious path that's dictated by the science, the Labour government is acting to ensure those cuts can be achieved. It will need a revolution in the way we live: in our homes, in the energy we use and in the way we move around. This government has made significant shifts in all of these areas. The progress we make shows that we can tackle climate change and also meet another key goal for the Labour party – fairness.

Last year the government's Warm Front scheme insulated a home every six minutes. In 2007-8 £350m was spent not just reducing carbon emissions but supporting those who need help most. We are also embarking on the Great British Refurb; by regulating the energy companies we are insulating 6m homes between 2008 and 2012, with every suitable loft and cavity being insulated by 2015. A quarter of British homes should have had full eco-makeovers and every home will have a smart meter by 2020.

In our power sector, we have a target – to generate 15% of our energy from renewables by 2020; this is challenging but achievable. It will include introducing feed-in tariffs to enable households to claim guaranteed cash back when they generate their own electricity, and incentives for renewable heat such as solar power. The biggest offshore wind farm in the world, the London Array, will now go ahead as a result of our intention to increase support for offshore wind in the . Wind last year provided the electricity for 2m homes.

The Greens dogmatically refuse to accept other forms of energy that can help us decarbonise our energy supply. We have insisted that no new coal power stations can be built without carbon capture and storage – the only country in the world to do this. Christian Aid said the decision was "courageous and progressive" but the Green party leader has said such efforts should be left to the market. Vital technologies such as CCS will not be built at commercial scale if left to the market, and countries such as China and India, who get two thirds of their power from coal, would not be able to move to low-carbon growth.

Climate change demands investment in all the renewables and new technologies like CCS and we also need to use proven ones and that means nuclear, even for those of us who opposed it in the past. Labour's commitment to the trinity of energy sources, clean fossil fuels, nuclear and renewables, means we can be serious not only about decarbonising the energy supply of the UK without the lights going out, but also the UK can have the edge when it comes to developing green manufacturing and jobs. In the teeth of a recession we had a budget which found £1.4bn for new investment in developing a low carbon economy. More than 20% of public investment since last November has been on sustainable and green projects.

As well as the revolution in power, and the Great British Refurb in our homes, we need a revolution too in transport. The UK has led in the EU to set the toughest mandatory car emissions standards in the world, and to accelerate the commercialisation of electric vehicles. And we have imposed the toughest emission standards for aviation in the world. Crossrail, increasing rail capacity and more local control of bus services, the list of Labour action on sustainable transport goes on: real programmes right now making a real difference to carbon emission reductions and improving people's lives.

The risk of defeatism is at its greatest when it comes to getting an international agreement. Only months ago people said it wouldn't be possible to get a global climate deal in Copenhagen this December. President Obama has transformed the debate. China is increasingly coming on board. The UK's efforts at home make a difference on the world stage and we are working hard to get that global climate deal.